Mold for tubular plastic parts



J Am!" y 1954 H. F. REICHENBACH 2,683,899

MOLD FOR TUBULAR PLASTIC PARTS Filed March 15, 1951 2 Sheets-Sheet 1FIGI.

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20 l 73% j INVENTOR. 10 $0 mimew-reflclmvanew 4 7' TOENEX y 1954 H. F.REICHENBACH 2,683,899

MOLD FOR TUBULAR PLASTIC PARTS Filed March 15, 1951 2 Sheets-Sheet 2 F|G.6. F IG.7.

FIGIO. FIG] I.

. INVENTOR. MDMQD EEE/CHE/VBAt/l Patented July 20, 1954 MOLD FOR TUBULARPLASTIC PARTS Howard F. Reichenbach, Waterbury, Comm, as-

signor of one-half to Cresale Incorporated, Waterbury, Conn, acorporation of Connecticut Application March 15, 1951, Serial No.215,688

2 Claims.

lhis invention relates to molds for the manufacture of plastic articlesand is more particularly directed to molds for accurately formingintegral inner sleeve and base units or the kind em ployed in swivel Orelevator type tubular cosmetic applicators.

In the mass production of small thin-walled tubular articles of plasticby the injection molding process, it has been found difficult toaccurately control the wall thickness due to the fact that the plasticmaterial injected into the mold at great pressure often had. a tendencyto build up more rapidly at one side within the mold than at the other,which resulted in a slight displacement of the mold core and consequentirregularity in the shell wall thickness or" the parts molded. Since itis necessary that the sleeve thickness be uniform for smooth operationof the assembled cosmetic applicator, as will more clearly be apparentfrom the following description, the use of ordinary molds constructed inaccordance with previously known techniques resulted in a high rejectionpercentage and consequent waste due to unusable parts.

Accordingly, one object of the present invention is to furnish a moldfor the manufacture 0f plastic parts of the character described whichincorporates means for maintaining the mold core in axial alignment evenwhile under the stress of unequal forces occurring during thehigh-pressure plastic injection operation.

Another object of the present invention is to provide a mold for themanufacturing of headed tubular plastic parts havin uniformwall-thickness and concentricity within close tolerances.

In the manufacture of cosmetic or lipstick applicators of the characterdescribed, it is often desirable for commercial reasons to change theshape or style of the visible base or head of the integral inner sleeveand base unit, without necessarily changing the concealed inner sleeveor tubular portion, Since the usual expedient of making an entirely newmold just to change the shape of a small portion of a molded article isa very costly procedure, it is accordingly another object of the presentinvention to provide a 1 With these and other obj sets in view, therehas been illustrated on the accompanying drawings one form in which theinvention may convenient- 1y be embodied in practice.

In the drawings:

Fig. 1 represents an inside view of the bottom half or" the mold takenalong the parting line l| of Fig. 3 looking in the direction of thearrows, the core plug being shown withdrawn to the right.

Fig. 2 is an inside View of the top half of the mold taken along theparting line 2-2 of Fig. 3, the core plug not being shown in this view.

Fi 3 is a vertical cross-sectional view of the closed mold with the coreplug shown in closed position. ready for injection of the plasticmaterial.

Fig. 4 is a front elevational view of a plastic cosmetic applicator partformed by the mold.

Fig. 5 a rear elevational view of the same.

6 is an elevational View of the cosmetic carrier of the lipstickapplicator.

Fig. 7 is a top view of the same.

Fig. 8 is an elevational view of the helically grooved propelling sleeveof the lipstick applicator.

Fig. 9 is an elevational view of the outer sleeve of same.

Fig. 10 is an assembly view in elevation of the lipstick applicator.

Fig. 11 is an elevational view of the cap or cover it appears whenfitted on the applicator.

Referring now to the drawings, in which like reference numerals denotecorresponding parts throughout the several views, the numeral In (Fig.3), indicates generally the mold embodying the invention, the samecomprising a lower die body i l, a complementary upper die body I2, anda removable core plug 53. Fig. 1 shows the inner side or" the lower diebody I l together with the partially withdrawn core plug it separatedfrom the upper die body [2.

It will be evident that though the particular mold herein disclosed isdesigned to lorm four of the tubular plastic parts shown in Figs. 4 and5, during a single cycle of operation, the invention is equallyapplicable to molds for forming any other number of tubular articles atonce.

The lower and upper die bodies M, iii are provided with a plurality ofaligned identical semicylindrlcal concavities i4, 55 respectively. forforming the outer wall It of the tubular parts H. A pair ofcomplementary head-forming blocks 1-3, I9 are closely embraced withinthe elongated rectangular openings 2t, 25 of the lower and upper diebodies H, l2 respectivel said. head blocks having therein complementarysemi-cylindrical identical concavities [4a, i5a of greater diameter thanthe concavities i i, [5 and aligned therewith respectively for forming acylindrical head 22 on each of the parts [1. The head forming blocks i3,i9 are secured within their respective die bodies by counter-sunkmachine screws 23, whereby said blocks may readily be removed forreplacement by other head-forming blocks (not shown) for manufactur ngplastic parts of different head size or shape by the use of the samebasic mold.

The plastic part I? is provided with a longitudinal slot 24 having areduced end opening or neck 25, for the formation of which there isprovided in each of the concavities iii of the upper die body ii, acentrally disposed longitudinal shoulder rib 26 having an end portion 21of reduced width.

Th lower and upper die bodies ll, i2 are provided with complementaryrectangular guide channel concavities 28, 29 respectively, for slidablyembracing the body of the core plug l3.

The core plug I3 is provided with four guide pins 38, so positioned asto be slidably received within the respective cylindrical guide channelsformed by complementary pairs of semi-cylindrical concavities 3|, 32 inthe die blocks.

Each of the guide pins 36 is provided with a coaxial cylindricaloutwardly-extending plug portion or core 33, of lesser diameter thanthat of the semi-cylindrical concavities 14, I5, whereby when the coreplug I3 is closed into the mold for a molding operation, as representedby the dotted line position thereof in Fig. 1, hollow plastic parts willbe formed thereby.

It is to be noted that the semi-cylindrical concavities Si, 32 arecoaxial with and of slightly greater diameter than the respectivesemi-cylindrical concavities l4, H: of the mold bodies, and that whenthe core plug is at its innermost or molding position the outer ends ofthe uide pins 36 do not quite reach the ends of the complementaryrespective concavities l4, 15, whereby a peripheral shoulder 34 will beformed on the L molded tubular parts H (see Figs. 4 and 5).

In order to hold the plug portions or cores 33 securely against bendingdue to forces incidental to the plastic injection operation, each of thesemi-cylindrical concavities I4 is provided at its inner end with acentral upstanding positioning lug 35, concavely hollowed at its upperend so as to slidably embrace the inner end of said plug portions 33. Itwill be thus clearly evident that the combined restraining action of thelongitudinal shoulder ribs 26 and the lugs 35, acting against oppositesides of the plug portions 33, will effectively counteract any tendencytoward axial displacement of said plug portions.

The improved mold is further provided in its lower die body with theusual plastic injection orifice 36, and the concave injection flowchannels 3'! having portions communicating with each of the moldingcells.

Operation of the mold In a molding operation, the die body members ll,l2 will be held together and the core plug l3 will be moved into closedposition in the mold H) as shown in Fig. 3, after which the fluidplastic cores 33 will be held rigidly in axial alignment, whereby aconcentric plastic shell will be formed. After the plastic has set, themold will be parted and the core plug l3 withdrawn, whereupon the usualejector pins 38, extending through the lower die body H and openingflush into the molding cells at opposite ends thereof, will be struck attheir outer ends to dislodge the formed plastic parts. It will be notedthat the presence of the positioning lug 35 in the mold cells will leavea small rectangular opening 39 in the outer wall it near the cylindricalhead 22 of the formed parts H.

The lipstick applicator embodying the tubular part or inner sleeve llformed by the mold further comprises a lipstick carrier 58 (Figs. 6 and'7) a propelling sleeve 4! (Fig. 8), an outer sleeve 42 (Fig. 9), and ahemispherically domed cap member or cover 43 (Fig. 11)

The carrier 40 which is preferably struck from sheet metal, is cupshaped, and has a cylindrical wall 14 of such a diameter as to slidablyfit within the inner sleeve IT. The wall 44 of the carrier M is providedwith an aperture within which is force-fitted a headed pin 45 extendinglaterally therethrough, said headed pin serving both to anchor thelipstick and guide the carrier vertically within the slot 24 of theinner sleeve 17.

The propelling sleeve 4 I, also preferably formed of sheet metal,rotatably embraces the outer wall it of the inner sleeve IT, and isprovided with a helical slot 46 within which the head of the pin 45 isdisposed in the assembled applicator.

The outer sleeve 42 frictionally embraces the propelling sleeve ll andserves to hold the same rotatably disposed on the inner sleeve llbetween the facing undersides of the head 22 and the shoulder 3d.

Fig. 10 illustrates an assembly view of the applicator in which alipstick L is shown in dashed lines. The cap member 43 is provided tocover the lipstick when the applicator is not in use, as illustrated inFig. 11. The applicator is operated by merely removing the cap 63 andthen turning the head 22 with respect to the outer sleeve G2, whereuponthe helical slot 46 on the propelling sleeve ll will be rotated withrespect to the longitudinal slot 2-; to urge the headed pin :25, thecarrier 4!), and the lipstick L inwardly or outwardly depending upon thedirection in which the head is turned.

It is to be noted that since the head of the pin must be long enough tobe engaged by the thin edges of the helical slot i6 and the propellingsleeve ll, and since the outer end of said head must at the same time beshort enough so as not to rub against the inner surface of the outersleeve 42, it is required that the concentricity of the tubular wallsurfaces be very accurately maintained. The improved mold hereindisclosed and embodying the invention has been found to be exceptionallywell suited to meet this requirement.

One advantage of the improved mold is that it makes possible the massproduction of accurately molded tubular parts with a minimum rejectionratio and consequent lower inspection costs.

Another advantage of the improved mold resides in the fact that plasticarticles having portions of different shape may be manufactured by useof the same basic mold.

While there has been disclosed in this specification one form in whichthe invention may be embodied, it is to be understood that this formisshown for the purpose of illustration only, and that the invention isnot to be limited to the specific disclosure but may be modified andembodied in various other forms without departing from its spirit. Inshort, the invention includes all the modifications and embodimentscoming within the scope of the following claims.

Having thus fully described the invention, what is claimed as new, andfor which it is desired to secure Letters Patent is:

1. In a die set for molding a tubular plastic article, the combinationcomprising a lower die body, an upper die body, both of which are openat one end, said die bodies having aligned complementary elongatedsubstantially semi-cylindrical concavities for Shaping the outer wall ofa tubular article to be molded when said die bodies are in face-to-facerelation, a cylindrical overhung core member coaxially slidable into theopen end of said die set between said concavities, and rigidly securedat its outer end to a core plug, an elongated rib on one of said diebodies projecting inwardly into engagement with said slidable coremember, and a short lug on the other die body located diametricallyopposite said rib for engaging the inner end of said core member whenthe latter is in its innermost position and a head-forming block spacedfrom said core member when in its innermost position whereby the wallsof said tubular plastic article will be exactly concentric and uniformin thickness.

2. The invention as defined in claim 1, in which said head-forming blockcomprises a pair of removable complementary sections having alignedcavities to form the head of said tubular plastic article, said blocksections being closely embraced within positioning cavities at the innerends of their respective die bodies.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,692,340 Lattin Nov. 20, 1928 1,787,503 Zube Jan. 6, 19312,181,558 Beckman Nov. 28, 1939 2,296,016 Bostwick Sept. 15, 19422,351,395 Broder June 13, 1944 2,523,457 Thompson et al. Sept. 26, 1950

